I would choose Toledo. Not becasue it is "better" but it is smaller, more approachable, and really delightful in th eevening when the day-trippers have left. One night is not enough to do justice to Sevilla.

There is no city in Spain, and few elsewhere in the world, that offer the historical sweep of Toledo. You can literally visit sites that span the Visigothic period to El Greco to the Spanish Civil War in a single day. And no other city preserves the art/architecture of Medieval Iberia's three cultures (Muslim, Jewish, and Christian) like Toledo does. The AVE from Madrid's Atocha takes only 33 minutes. Be sure to get a good map (preferably before arriving) so you can plan your visit.

I prefer Toledo, for many reasons. But I am not willing to say to a stranger that she will prefer it too. They are different enough that you can get a general idea from a guidebook and make a choice based on that.

I would agree that Toledo has "better" history and a superior cathedral to Segovia. However, the aqueduct is stunning, and if you love food, Segovia is the home of roast suckling piglet. Restaurants Jose Maria has a good suckling pig.

Segovia is a nice place too, but wasn't one of the options. As much as I like Sevilla, it really needs more than just one night. You'd spend half a day getting there and lose a few more hours going to Costa del Sol. The Alcazar alone can take 3-4 hours to do it justice. So I'd pick Toledo, which many people do in a day. An overnight gives you a lot more time to enjoy and it calms down a lot after the tour busses leave. And it has an amazing range of history, culture and architecture.

You can not go wrong with either choice. I love both!! For one only though I would go for Toledo for the reasons mentioned by others. Take a route such as this: Train from Madrid (Atocha) to Toledo...25 minutes, no stops. In Toledo get a taxi to the Cathedral. Get the hand held audio guide and the tour will take 1 - 2 hours depending on how long you stay at each stop along the way. From there walk to the Plaza Zodocover, the main plaza, Go through "the keystone arch" and down the steps past the statue. Turn left and straight ahead is a wonderful outdoor cafe. After lunch, go next door to the Muzeum de Santa Cruz. Excellent exhibits which change from time to time. From there turn right back to the corner and then up the hill to the military museum. Opened last year, it has more than military items. Built in and under Toledo's Alcazar. Or walk or taxi to St. Tome Church and from there to The House of El Greco- very nice. Get a taxi back to the station.